Think You Need New Machine Heads?
Don't Replace, Restore!
PROJECTS GUITAR MAINTENANCE
Restoration Projects: Machine heads
Often a customer will tell me they need the machine heads changing on their guitar. I never doubt them when they have bought a new, budget guitar. Yeah, lets mod the hell out of it. But when the guitar is a vintage guitar of merit, with it's original tuners … then I feel it's my duty to revive the originals wherever possible.
It's possible to bend shafts back to something like straight too, by clamping the plate in a vice and using pliers to carefully bend them back. You have to make a judgement on this though as a bent tuner is often better than no tuner, or a mis-match.
When tuners are stiff, the problem could be mechanical, i.e. something had broken and is jamming the gears. But it is more likely that the grease has hardened, and thickened with dust, tiny shards of metal, etc. which will need to be cleaned out as much as possible. Of course it's impossible to know for sure as you can't see inside. Closed tuners cannot usually be taken apart because the tabs holding the back to the base plate are highly likely to snap either on removal or refitting. The course of action is to follow a 'most probable cause' and see if what works.
For the purpose of this essay I've photographed process using a tuner I'd relic'd years ago and never lubricated so the gears were completely stuck.
The tools I use to carry out this restoration are several small screwdrivers, a couple of 1.5mm lab. syringes, and a ultrasonic bath and a small bench vice. Consumables are sodium free cleaner (I use a base surfactant), distilled water, isopropanol, acetone, and red lithium grease.
Firstly I carefully remove the tuners using cross head or flat head screw drivers. I have a few on hand as the screws are going to have varying degrees of wear. Sometimes a small flat-head works best on badly damaged cross-head screws. If any are too worn to go back in, they will need to be replaced.
It's a good idea to leave the ferrules in place unless you're doing other work on the headstock.
Once the tuners are off, it's time to clean out the hardened grease and whatever else has worked it's way in there over the last 60-odd years. In order to get that crud out, I put them in the ultrasonic cleaner. The bath contains a solution 5% salt-free surfactant in distilled water. The solution is heated to 50 degrees Celsius to help dissolve the crud and I set the clear to run for 10 minutes (to remove the external rust leave in the bath longer until the rust is removed). The tuner will be cleaned inside and out, but some of the sludge will be trapped inside. In order to remove as much of the remaining sludge as possible I do a combination of flush and suck of isopropanol with a syringe. Acetone can also be used, by be careful not to melt any parts susceptible to acetone. The needle of the syringe needs to be small enough to fit through the grease hole on the back.
Once I've removed some grit, I test by turning the dry gears a little, flush, test, repeat until I'm happy the gears are as clean as they can be. I then draw some red lithium grease into a syringe and pump some of that through the aperture and onto the screw thread. Then I turn the tuner to deposit the grease onto the cog. Because want to get the grease on the underside of the cog I end up using a lot more grease than I would when servicing open tuners. It takes several turns of the mechanism to completely coat the thread and cog with the grease. I do this by hand so I can feel the dry spots.
Before refitting the tuners I turn the mechanism many times in both directions until the excess grease has worked its way out of any openings. When not more grease comes out, you can refit the tuners. You may want to use a mechanical winder to speed-up this part of the job.
Add a tiny dot of red lithium grease to the inside collar of the ferrules to negate any friction there. Now you can refit the machine heads and enjoy trouble free tuning until the next service.
I chose a really crusty tuner for demo purposes
The ultrasonic cleaner cleans inside the casing
Flushing with isopropanol
Red Lithium Grease
Using a syringe to pump grease into the tuner's gears
Maintenance on open tuners is just as important, but it's much easier to carry out.
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